This is the depiction in Robert's Slant Range tutorial...(is this the image you refer to Gene?)...



And here's a partial clip from Robert's tutorial...

The records below show a portion of sonar image before and after correction for slant range and speed distortions. Note that the feature closer to the sonar is changed more by the correction process than the features further away.

I think the important thing to take from this is that the SI image (Contour Mode On or Contour Mode Off) may not be a "true" representation of actual linear distances across the lake bottom....

This is because the xducer is always above the bottom (dictated by depth)...and because the unit may be applying "correction factors" (proprietary that only the brand knows)...

This is why waypoints marked on the SI image should always be verified (and remarked) with inspection from the "down pointing" 2d cones ...

Rickie